Splash Screen: 16/24 bits vs 16/32 bits; why?

Troubleshooting General Help
1

I was wondering, why, when I run a game in a window, I get asked to choose between 16 and 24 bits, and when running full-screen, I get asked to choose between 16 and 32 bits. Also, I know that both 16 and 24 bits are (normally) for RGB, while normally RBGA is 32 bits, so how does this all work in 16 or 24 bits, when I use textures with transparency? :smiley: If somehow, the “alpha” is optimized away when drawing to the screen, and so the screen does not need the “alpha bits”, then what goes in those additional 8 bits when drawing on a 32 bit screen?

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Maybe alpha. Maybe nothing. It’s about byte alignment since I guess in full screen you are essentially writing directly to the screen memory and in windowed mode the OS is somewhat in the middle.

I actually thought that when I traced through the code that the bits are completely ignored in windowed mode. I could be misremembering. Because I’ve definitely had alpha written to screen caps before and I always run windowed mode. So clearly it was a 32 bit buffer somewhere.

Generally alpha is not necessarily stored in the target. OpenGL can do it’s job without writing alpha but for a 32 bit buffer it does no harm to write it.

I could be completely making things up, too, but this has been what I’ve gathered from experience.

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isnt that for the depth buffer? And has nothing to do with alhpa and rgb(a) whatsoever?

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@Empire Phoenix said: isnt that for the depth buffer? And has nothing to do with alhpa and rgb(a) whatsoever?

Z-buffering - Wikipedia

Nope.

http://code.google.com/p/jmonkeyengine/source/browse/trunk/engine/src/desktop/com/jme3/app/SettingsDialog.java#575

http://hub.jmonkeyengine.org/javadoc/com/jme3/system/AppSettings.html#setBitsPerPixel(int)

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Wait, isn’t that the color depth of the screen device? What you ask the video driver to provide when it is rasterizing to be drawn on screen (video mode) http://lwjgl.org/wiki/index.php?title=LWJGL_Basics_5_(Fullscreen).

What format you use for textures (ARGB_8888 or whatever) when talking to OpenGL isn’t really relevant here, the video driver/HW will do what needs to be done to draw it to the screen using the video mode.

Or I’m making things up :slight_smile:

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@jmaasing said: Wait, isn't that the color depth of the screen device? What you ask the video driver to provide when it is rasterizing to be drawn on screen (video mode) http://lwjgl.org/wiki/index.php?title=LWJGL_Basics_5_(Fullscreen).

What format you use for textures (ARGB_8888 or whatever) when talking to OpenGL isn’t really relevant here, the video driver/HW will do what needs to be done to draw it to the screen using the video mode.

Or I’m making things up :slight_smile:

You have it right. It’s the color bit resolution of the target display.